Introduction to Transportation: Lecture 3

Corso di Sistemi di Trazione
Lezione 8: Ergonomia del
conducente e dei passeggeri
Lezione presentata dal Prof. F.Filippi
A. Alessandrini – F. Cignini – C. Holguin – D. Stam AA 2014-2015
Definizioni di Ergonomia
"Ergonomics (or Human Factors) is the
scientific discipline concerned with the
understanding of the interactions among
human and other elements of a system, and
the profession that applies theory, principles,
data and methods to design in order to
optimize human well-being and overall
system performance" International
Ergonomics Association (IEA).
Origine dell’ergonomia
Durante la II guerra mondiale era necessario
semplificare i comandi degli aerei per avere
un gran numero di piloti con pochi giorni di
formazione.
Successivamente l’ergonomia è servita a
migliorare la vita del lavoratore, l'efficienza e
l'affidabilità dei sistemi uomo-macchina.
L'obiettivo attuale è progettare oggetti,
servizi, ambienti di vita e di lavoro, nel
rispetto dei limiti dell'uomo, per migliorarne il
benessere e aumentarne le capacità.
The driving tasks
It can be complex and demanding on the driver.
For example, driving on an unfamiliar interstate
highway or having to take a detour due to an
accident.
Driving errors occur when the driver experiences
task overload or when the driver’s expectations are
not met.
For example, a left hand off-ramp on an interstate
when the majority of off-ramps are on the right side.
Providing sufficient information to the driver in a
timely fashion can help prevent driving errors.
The three levels of the driving task
Control:
Includes basic steering and speed control.
Guidance:
Includes road-following, car-following,
overtaking and passing, merging, lane
changing and responding to traffic control
devices, obstacle detection.
Navigation:
Includes trip planning and route following.
Performance of the driver impacts the
following design parameters
Sight passing distances
Lane widths
Location of traffic control devices
Speed limits
Traffic signal timing
Stopping sight distances
Roadside safety features
Components of Highway Mode
Need to understand the limitations and interactions
between
• Driver
• Pedestrian
• Vehicle
–
–
–
–
Heavy trucks
Passenger vehicles
buses
Bike (but may have separate facilities)
• Road
Design Driver
Wide range of system users
• Ages: 16 year old to 80 year old
• Different mental and physical states
• Physical (sight, hearing, etc)
• Experience
Performance of the driver impact
the following design parameters
Sight passing distances
Lane widths
Location of traffic control devices
Speed limits
Traffic signal timing
Stopping sight distances
Roadside safety features
Components of Highway Mode
Understand the limitations and interactions:
Driver
Pedestrian
Vehicle
• Heavy trucks
• Passenger vehicles
• buses
• Bike (but may have separate facilities)
Road
Human Characteristics
Perception – Reaction Time
Visual Reception
Walking Speed
Hearing Perception
Actions taken by drivers depend on their
ability to receive, evaluate, and respond to
situations ( Ex.: dog darting into roadway)
Wide range of system users
Ages: 16 year old to 80 year old
Different mental and physical states
Physical (sight, hearing, etc)
experience
La variabile tempo
Il sistema U-M-A deve considerare:
• Il tempo reale dell’uomo che opera con le
macchine in un determinato ambiente
• Il tempo delle prossime ore in cui
subentrano fenomeni di adattamento e
stanchezza
• Il tempo lungo degli anni in cui si
manifestano fenomeni di obsolescenza
professionale, diminuzione delle capacità,
stanchezza dovuta alla routine.
Human performance in traffic
The fundamental parameters in human
performance are largely centred around
neuromuscular and cognitive time lags.
These are perception – reaction time,
control movement time, responses to the
presentation of traffic control devices,
responses to the movements of other
vehicles and to hazards in the roadway.
They are related to the different segments of
the driving population.
Visual reception (acuity)
Static (stationary objects):
• Depends on brightness
• Increases with increasing brightness up to ~ 3
candles (cd/sq ft) and remains constant after that
• Contrast
• Time (0.5 to 1.0 second)
Dynamic (ability to detect moving objects)
• Clear vision within a conical angle 3° to 5°
• Fairly clear within 10° to 12°
Peripheral Vision
Ability to see objects beyond the cone of
clearest vision (160°):
• Age dependent
• Objects seen but details and color are
not clear
Cone of Vision
Impegno spaziale del conducente
La forma e l’estensione della zona rigata di impegno
spaziale del conducente è funzione della velocità, raggio
di curvatura e distanza di frenatura e interagisce con il
tempo di reazione.
1 secondo
2 secondi
3 secondi
Sfondo
4
Visibilità del conducente
3
2
1
4
3 2
1
Autostrada v = 100 km/h
1. Zona di illeggibilità, moti
di traslazione
2. Campo di visibilità
periferica, moti apparenti
di rotazione e traslazione
3. Cono di concentrazione
dell’attenzione, campo
statico
4. Sfondo, macroelementi
del paesaggio
Color Vision
Ability to differentiate one color from another
• Lack of ability = color blindness
• Combinations to which the eye is the most
sensitive
– Black and white
– Black and yellow
Vision
20/20 can read 1/3 inch letters at 20'
Example: a driver with 20/20 vision can see a sign from a
distance of 90 feet if the letter size in 2 inches.
How close would a person with 20/50 vision have to be to
see the same sign?
X = (90 feet) * (20/50) = 36 feet
How large would the lettering have to be for a person with
20/60 vision to see the same sign from 90 feet?
h = 2 inches (60/20) = 6 inches
Glare Vision
Glare Vision results in a decrease in ability for a driver to see
and causes discomfort for the driver.
Glare Recovery is the time it takes for a driver to recover
from the effects of glare after passing a light source.
Research has shown that the time to recover from dark to
light conditions is 3 seconds and 6 seconds to recover from
light to dark conditions.
Glare Vision is a problem for older people who drive at night.
Glare effects can be minimized by reducing the brightness of
lights and positioning lights further from the roadway and
increasing the height of the lights.
Glare Recovery
Ability to recover from the effects of glare
• Dark to light : 3 seconds - headlights in
the eye
• Light to dark: 6 seconds – turning lights off
• Usually a concern for night driving
Need to provide light transitions
Aging’s impact of vision
Older persons experience low light level
– Rules of thumb – after 50 the light you can
see halves with each 10 years
Glare – overloading eye with light
– Older drivers can take twice as long to
recover from glare
Poor discrimination of color
Poor contrast sensitivity
Depth perception
Ability to estimate speed and distance
• Passing on two-lane roads
• Judging gaps
• Signs are standardized to aid in perceiving
distance
Very young and old have trouble judging gap
Perception-Reaction Process
Perception
Identification
Emotion
Reaction (volition)
What is it?
A deer
Better
stop!
Typical Perception-reaction Time (PRT) range 0,5 to 7 s
Perception-Reaction Process
4 stages:
Perception
– Sees or hears situation (sees deer)
Identification
– Identify situation (realizes deer is in road)
Emotion
– Decides on course of action (swerve, stop, change
lanes, etc)
Reaction (volition)
– Acts (time to start events in motion but not actually do
action)
Foot begins to hit brake, not actual deceleration
Perception-Reaction Process
Perception:
• Seeing a stimulus along with other perceived objects.
• Out of the corner of your eye you see something coming out of the
woods towards you.
Identification:
• Identification and understanding of the stimulus. Alternatives are
developed.
• You realize that it is a deer about to cross the highway in front of
you. Do you swerve to miss it? Can you stop in time to miss it? Do
you speed up to miss it?
Emotion:
• Judgment is made as to the proper course of action. A decision is
made.
• You decide the best course of action is to swerve and hopefully
miss it.
Volition:
• Reaction or execution of decision
PRT
Determined from research:
• 0.5 seconds to 0.75 seconds for most driving tasks.
• 0.5 seconds up to 4 .0 seconds for complex driving
tasks.
PIEV times are dependent upon the driver’s rest,
influence of alcohol and/or drugs.
AASHTO Design values:
• 2.5 seconds for computing stopping sight distances.
• 2.0 seconds for intersection sight distance due to the
“degree of anticipation” of the driver approaching an
intersection.
Driver's braking response
Prior to the actual braking of the vehicle
there are two steps:
1. the perception-reaction time (PRT);
2. the movement time (MT ), immediately
following.
Response to the vehicle ahead
The rate of change of visual angle triggers a
warning that an object is going to collide.
Human visual perception of acceleration of an
object in motion is very gross and inaccurate.
It is very difficult for a driver to discriminate
acceleration from constant velocity unless the
object is observed for 10 or 15 sec.
The major cue is rate of change in visual angle
with thresholds normally distributed between
3x10-4 e 10x10-4 radians/sec.
Lognormal Distribution of P-R Time
Probability density function The log-normal probability
density function is widely used
in quality control engineering
and other applications in which
values of the observed
variable, t, are constrained to
values equal to or greater than
zero, but may take on extreme
positive values, exactly the
situation that obtains in
considering P-R time.
PRT
Chaining Model of PRT
Component
1) Perception latency
Time Cumulative Time
(sec)
(sec)
0.31
0.31
Eye movement
0.09
0.40
Fixation
0.20
1,00
Recognition
0.50
1.50
2) Initiating brake application 1.24
2.74
The PRT Factors
Environment:
• Urban vs. Rural
• Night vs. Day
• Wet vs. Dry
Age
Physical Condition:
• Fatigue
• Drugs/Alcohol
PRT Factors
medical condition
visual acuity
ability to see (lighting conditions, presence of fog,
snow, etc)
complexity of situation (more complex = more
time)
complexity of necessary response
expected versus unexpected situation (traffic light
turning red vs. dog darting into road)
Aspettativa e tempo di reazione
Il ruolo dell’aspettativa è fondamentale per
la comprensione del comportamento del
conducente.
Es. il tempo di giallo ai semafori
Esperimenti sul tempo di reazione per
frenare nel caso di situazione improvvisa (A)
e con avviso (B).
A) mediana 0,73 s variabile tra 0,5 – 1,1 s
B)
0,54
0,4 – 0,8
Blood Alcohol Concentrations BAC
Driver Impairment at Various BACs
DAT (Divided Attention Test) Raw Scores, all subjects
(N = 168)
How are these factored into design?
Design criteria must be based on the
capabilities and limitations of
1) Best drivers
2) Average driver
3) Worst drivers
Il posto di guida
Area di ottima acuità visiva
Area di ottima acuità visiva
Visibilità dei controlli e display
Area entro cui i display principali
devono essere collocati
Posizioni raccomandate dei
segnali di allerta visivi
Area di normale e massima presa
Esempio di tre display elettronici
per la velocità
Circolare
Orizzontale e verticale
Digitale
Posture di conducenti
A e B sono una cattiva postura con affaticamento del disco.
C è la postura buona con il peso distribuito uniformemente.
Forme variabili del supporto lombare
determinate dalla camera A, B e C
Progetto di postura per autista
Paretina
bus
trasparente
Coni di
visibilità a
sedile tutto
indietro
51
Sezione
52
Comfort nei mezzi di trasporto collettivo
Fattori del comfort:
• Aspetti dinamici
• Ambiente interno
• Spazio
Aspetti dinamici
Passeggero in piedi tenuto confort
Non
Non
confort accettabile
Accelerazione e dec. m/s2
Longitudinale
1,0
2,0
4,0
Componente orizzontale
0,8
1,5
3,0
Componente verticale
0,2
1,0
2,0
Contraccolpo m/s3
0,6
1,0
1,5
Ambiente interno
confort
Non
confort
Non
accettabile
20 – 22
12 – 35
< 12 > 35
Umidità (%)
50
< 30 > 70
< 30 > 70
Ventilazione m3/h-pass
35
< 20
<8
Rumore dBA
< 65
75 – 85
> 85
Vibrazioni mm/s
0,2
1,2
3,0
Temperatura (°C)
Spazio
confort
Densità (pass/m2)
Umidità (%)
Ventilazione m3/h-pass
Non
Non
confort accettabile
2–3
>3
>6
15 – 25
> 25
> 200
1–2
< 1,0
< 0,2
Human-Capable Design
Creating products that expose users to less
mechanical stress in order to:
• Decrease risk of operator injury
• Increase operator performance
(efficiency)
• Allow operators to safely and comfortably
interact with products longer
System Safety reviews
• Considers risk of injury to human
• Tendency to focus on equipment failure
conducted during design phase of the
product development cycle
• Strive to identify and mitigate injury risks
before products are deployed
• Alternative is expensive retro-fits
• May not optimize design to avoid features
that compromise human performance
Methods & Techniques Employed
• Preliminary Hazard Analysis
• Failure Mode and Effect Analysis
• Fault Tree Analysis
• Management Oversight & Risk Tree
• Energy Trace and Barrier Analysis
Limitations of Approach
• Struggle to Capture the “Human Side”
• System Safety tools dependent upon
assessor’s knowledge of human
capabilities
• Analyses are not structured in a way that
obligates users to consider long term
effects on human operators
• Tend to be “product-oriented” at the
expense of the human system component
Common System Design Errors
Dimensional Incompatibility
Sizing
• Human-Machine Couplings
• Wearables (headgear & clothes)
Accesses
• doors/hatches & portals
Reaches
• arms & legs
Example: Access Dimensions Problem
Pilots Killed
Ejecting From
F104A
Cause: Bad
Seat Design
F105D “Sample” Cockpit
Example: Poor Workstation Design
Shortened
muscles
compress
nerve
Excessive Reach
Requirement.
Bike Design Causes
Headaches.
Detail: Chronic
extended neck
posturing shortens
muscle in back of neck,
increases pressure on
suboccipital nerve, and
may cause headaches
& disc disease
Common System Design Errors
Excessive Metabolic Demand
Regional Fatigue
Overusing smaller muscles within a specific
region of the body
Systemic Fatigue
Overusing larger muscles from multiple body
regions
•
•
Activity stresses heart & lungs
Heat stress may contribute to overall
metabolic load
System Safety and
Human Systems Integration (HSI)
Both require risk identification
System safety has focused on risks to
systems
Human Systems Integration focus on design
for user
Develop Better Risk Assessment Tools
Based on human capability and exposure
tolerance limits for these common problem areas:
• Excessive Muscular Exertion
• Extrinsic External Load
• Excessive Metabolic Demand
• Dimensional Incompatibility
• Extrinsic Mechanical Energy Exposure
Design engineers can use them to guide decisions
during early product development.
Procurement of Heavy Vehicle
Risk Analysis Reveals Following:
• Vehicle operation exposes personnel to
whole body vibration
• Purchase decision should consider injury
risk based upon existing standards
1.6
1.1
0.9
Sistema U-M
Segnali
video
Decisioni
Percettori
Processo
Attuatori
68
Driver task analysis in real time
Le informazioni nel sistema U-M
MACCHINA
ACCUMULO INFORMAZIONI
INGRESSO
PERCEZIONE
ELABORAZIONE
E DECISIONE
AZIONE
UOMO
ACCUMULO INFORMAZIONI
PERCEZIONE
ELABORAZIONE
E DECISIONE
AZIONE
ACCUMULO INFORMAZIONI
CONTROLLO
PROCESSO
PROCESSO
USCITA
Confronto Macchina Uomo
La macchina è migliore nel:
• Rispondere con velocità, potenza, precisione
• Immagazzinare e richiamare informazioni
• Eseguire compiti monotoni il rispetto degli standard
• Elaborare le informazioni in modo deduttivo
• Cancellare completamente informazioni dalla memoria
• Eseguire simultaneamente compiti diversi
L’uomo è migliore nel:
• Riconoscere forme e modelli
• Immagazzinare e richiamare informazioni rilevanti
• Improvvisare
• Ragionare in modo induttivo
• Esprimere giudizi di valore
Livelli di automazione nel processo
decisionale
1. L’uomo (U) prende in esame decisioni alternative,
sceglie e attua una decisione.
2. Il computer (C) propone un insieme di decisioni
alternative, U lo può ignorare nel prendere ed attuare
una decisione.
3. C propone un limitato numero di decisioni alternative, U
sceglie una di queste.
4. C propone un limitato numero di decisioni alternative e
ne suggerisce una, U può accettare o respingere, ma
ne sceglie una e la attua.
5. C propone un limitato numero di decisioni alternative e
ne suggerisce una che C attuerà se U approva.
Livelli di automazione nel processo
decisionale
6. C prende la decisione e informa U in tempo perché
possa fermare l’attuazione.
7. C prende e attua la decisione, informa U, ma
successivamente.
8. C prende e attua la decisione, informa successivamente
U se richiesto da U.
9. C prende e attua la decisione, informa successivamente
U se lo ritiene necessario.
10. C prende e attua la decisione in completa autonomia.
Automated functions on cars
Two functions
lateral control
longitudinal control
Cruising and collision avoidance